Chromatin is dispensable for bacterial life
Inside cells, DNA is intimately associated with proteins, forming chromatin. The protein constituents of chromatin vary across the tree of life: histones are the principal building blocks of chromatin in eukaryotes and many archaea, whereas bacteria typically encode a collection of nucleoid-associated proteins (NAPs) that wrap, bend, bridge or coat the DNA. Although chromatin proteins appear to…
Chromatin, a complex of DNA and proteins, is traditionally considered an essential component of cellular life. In eukaryotes, histones are the primary building blocks of chromatin, while bacteria possess nucleoid-associated proteins (NAPs) that perform similar functions.
Despite chromatin proteins being ubiquitous among cellular life forms, experiments suggest that DNA-templated processes like transcription, replication, and DNA repair may occur without chromatin. To investigate this hypothesis, researchers created a strain of Escherichia coli (E. coli) lacking nine of its most abundant NAPs, resulting in a cell devoid of its native chromatin, referred to as ({Delta}NAP9).
Through a variety of techniques, researchers explored the impact of ({Delta}NAP9) on the cell's chromatin structure, composition, and overall functionality. The results showed that ({Delta}NAP9) did undergo alterations, with a notable global dysregulation of gene expression. The transcriptional output across the entire genome became homogenized, akin to the effects of histone depletion in eukaryotic cells.
These findings emphasize the role chromatin plays in compartmentalizing genomic information, allowing for localized suppression of selfish elements and dynamic changes in genome activity in response to environmental shifts. Nevertheless, the successful creation of ({Delta}NAP9) demonstrates that bacteria can survive and perform basic cellular functions without co-evolved chromatin proteins. This discovery opens up possibilities for the radical re-engineering of prokaryotic chromatin and gene expression systems.
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